Add poll n wait for remote deps (zookeeper, cassandra, etc) on midonet api host

[nephomaniac]

It's likely the zookeeper/cassandra services may not be hosted on the same machine hosting the Midonet API. In this case the zookeeper service will need to be installed and running on the zk hosts otherwise the midonet RB will fail for the api host.
For Calyptos purposes, some ideas:
-Run the zookeeper RB in an earlier phase of the deployment.
-Could add a retry/backoff/timeout either polling for zk state, or just retrying that code block, etc.
Thanks,
-M